蒸散包括了蒸发与蒸腾，是一个受生理过程和物理环境作用的复杂过程，具有很大不确定性，这种不确定性的原因及其机理并不完全清楚，特别在全球变暖情形下。过去的研究更少见于湿润区，本项目选择华南湿润区森林生态系统为研究对象，于鼎湖山国家野外生态定位研究站设计了严格控制水循环过程的森林生态系统移位实验平台，该大型增温平台为研究蒸散的不确定性提供了条件。本项目研究不同温度环境下生态系统优势树种冠层导度和蒸腾速率、林分尺度上蒸腾量及蒸腾对叶面积指数季节变化的响应、不同森林冠层与大气之间的水分交换特点、不同林型树种的水分利用效率特征，不同生长阶段森林蒸散差异。综合评估南亚热带湿润区森林生态系统土壤-植物-大气连续体的水分交换能力及其在蒸散能力上的响应特点，揭示气温上升情形生态系统蒸散的生物、物理调控机制。通过本项目的研究，我们试图在生态系统水平上弄清楚水资源与植被变化机理，阐明气温上升与水资源的水文学联系。

Evaporation and transpiration are the two components of evapotranspiration，due to the complexity two variables, evapotranspiration is a very complicated continuous process that regulated by plant physiological processes such as photosynthesis and physical environment, e.g temperature rising, it shows a lot of uncertainties. Up to date, all these uncertainties and the mechanism are not so clear in context of global warming. Comparing to the studies on arid or semi-arid region, previous studies on evapotranspiration are very scare in humid regions. Our project focuses on typical forest ecosystems in a humid southern China, and set up experimental sites at the Dinghushan Forest Ecosystem Research Station, we have established the experimental platform of forest ecosystems transplanted down an elevation gradient, which accurately controls the hydrological process. This big well designed field warming experiment platform is very favorable to determine the uncertainty of evapotranspiration. The main contents of the research are: (1) to study canopy conductance and transpiration rate in different forest types and different artificial temperature controlling conditions along the elevation, (2) to study the response of transpiration and its capacity to the seasonal changes of the leaf area index at stand scale, (3) to quantify different forest canopy and the atmosphere exchange characteristics of different forest tree species in water use efficiency, and quantify the contribution to evapotranspiration in different growth stages, (4) to assess the water-vapour exchange and its response to evapotranspiration capacity comprehensively in soil-plant-atmosphere continuum in humid region in lower subtropical China, and reveal biological, physical control mechanisms on evapotranspiration at plant ecosystem level under temperature rising. After carrying out this project, we will try to reveal the mechanism of water resources and water vegetation change, and clarify the linkage between temperature rising and water hydrology at the ecosystem level.